1. Field of the Invention
The present invention relates to a technique which uses pulsed laser light to inspect a semiconductor device and, more particularly, to a technique for increasing the electric field strength of an electromagnetic wave pulse generated from a semiconductor device in response to the irradiation of pulsed laser light to the semiconductor device.
2. Description of the Background Art
There have been proposed methods of detecting various defects, such as a defective location at a pn junction, and a break, a short circuit and a high-resistance location in an interconnect line, for the purpose of conducting a failure analysis and a fault analysis on semiconductor devices.
A known example of the technique of inspecting a semiconductor device is a technique which detects an OBIC (optical beam induced current) phenomenon. For this inspection in which a reverse-bias voltage is applied to a semiconductor device, it is necessary to perform a bonding process on the semiconductor device, thereby electrically connecting the semiconductor device to an external voltage application apparatus. In the course of the steps of manufacturing a semiconductor device, it is difficult to connect the semiconductor device to the external voltage application apparatus. A technique is hence proposed which inspects a semiconductor device in a non-contacting manner, as disclosed in Japanese Patent Application Laid-Open No. 2006-24774, for example.
Specifically, the inspection method disclosed in Japanese Patent Application Laid-Open No. 2006-24774 is a method which applies pulsed laser light to a semiconductor device to detect various defective locations. Upon receiving pulsed laser light, part of a semiconductor device where an electric field is present such as a pn junction generates an electromagnetic wave pulse. Based on the detection of the generated electromagnetic wave pulse, the detection of defective locations in the semiconductor device is performed. Such an inspection method is capable of inspecting a semiconductor device in a non-contacting method. This allows such an inspection method to handle a semiconductor device being subjected to the manufacturing steps as an object to be inspected.
In the inspection method disclosed in Japanese Patent Application Laid-Open No. 2006-24774, the inspection is conducted without the reverse-bias voltage applied to the semiconductor device for the purpose of accomplishing the inspection in a non-contacting manner. However, the electric field present inside the semiconductor device is relatively weak. The electric field strength of the generated electromagnetic wave pulse is accordingly extremely low. It is hence difficult to detect the extremely low electric field strength in some cases. For this reason, it has been necessary to decrease noise components by optimizing the apparatus configuration or the measurement conditions of an inspection apparatus, thereby improving the sensitivity of measurement of the electromagnetic wave pulse. Thus, preparatory operations require a large amount of time and complexity. A technique which improves the sensitivity of detection of an electromagnetic wave pulse in a non-contacting manner is therefore desired.